FHIRPath CLI

[lmsurpre]

Is your feature request related to a problem? Please describe.
Currently, java project can use our fhirpath implementation by

1. including a dependency like this:

<dependency>
    <groupId>com.ibm.fhir:fhir-path</groupId>
    <artifactId>fhir-path</artifactId>
    <version>4.3.0</version>
</dependency>

and
2. writing code like this:

FHIRPathEvaluator.evaluator().evaluate(resource, fhirpath);

This works ok, but I think would be cool to build an all-in-one shaded cli jar for our fhirpath module so that we can execute this more easily from the command line:

java -jar fhir-path-$VERSION.jar resource fhirpath

Describe the solution you'd like
Introduce a main that takes arguments for the resource content and the fhirpath string to execute.

Ideally, we could pass resource content from

• a file
• a string (raw command line arg); or
• stdin (so we can pipe to it)

One convention I've seen used is to interpret - as an indicator that we should read from stdin instead of a string or file, but I'm not tied to that.

Look at the fhir-persistence-schema and fhir-swagger-generator projects for examples on how to create the shaded all-in-one jar.

Describe alternatives you've considered
The alternative is to let clients do this themselves or use a different fhirpath engine for simple command-line stuff (e.g. the node fhirpath module).

Additional context
Add any other context or screenshots about the feature request here.

[lmsurpre]

It would also be nice to:

1. allow some way to pass jar files to extend the registry for fhirpath operations like memberOf; and
2. provide some way to see supplemental issues that were generated during the evaluation, maybe by printing those to System.error by default (with an option to suppress that)

[erodrago]

Would like to try out this issue @lmsurpre

[prb112]

@erodrago please go right ahead. if you have any questions, come find us on Zulip. https://chat.fhir.org/#narrow/stream/212434-ibm

[erodrago]

Alright thanks @prb112

[prb112]

PR #2130

[lmsurpre]

Confirmed that, after #2186, we now print usage info when invalid args are passed (and suppress the stacktrace by default):

$ java -jar fhir-path/target/fhir-path-4.7.0-SNAPSHOT-cli.jar
Error: Invalid parameters were set for the fhir path client
--path 'fhir-path'
--format ['json'|'xml'] . Default is 'json'
--file path-to-file . The file that is accessible and read.
--resource 'resource-payload'. The FHIR resource as a well formed string.
--pretty adds columns and start time and end time of the fhir path request
--throw-error print the stacktrace
--help

I also confirmed that I was able to invoke the cli via both stdin and also via file:

$ curl -s 'https://localhost:9443/fhir-server/api/v4/metadata' | java -jar fhir-path/target/fhir-path-4.7.0-SNAPSHOT-cli.jar --path 'CapabilityStatement.rest.resource.type.count()'
146

$ java -jar fhir-path/target/fhir-path-4.7.0-SNAPSHOT-cli.jar --path 'CapabilityStatement.rest.resource.type.count()' --file tmp.json
146

[lmsurpre]

Java isn't the best for quick little cli utilities like this because the JVM is still a bit heavy to start. I'd love to see if we could compile it to a native image using graalvm sometime...